1. Technical Field
The invention relates to a method for preparing nano silver particles. More particularly, the invention relates to a method for preparing nano silver particles with a particle size of 50 nm to 120 nm, in which the method is suitable for use in mass production of nano silver particles.
2. Description of Related Art
Since nano silver particles possess strong oxidant capacity to resist bacteria and viruses, they have shown great anti-bacterial and anti-virus effects and have become a popular topic of research in various fields. For example, much research is being conducted in the area of coating anti-bacterial materials with nano silver particles.
However, it is suggested in recent research that nano silver particles with a particle size smaller than 30 um would induce a serious bio-toxic effect on the human body and beneficial bacteria existing in nature. Therefore, the safety of nano silver particles with a small particle size has attracted much attention all over the world.
Generally, silver metal formed by a nanofabrication process may be referred to as nano silver particles. However, nano silver particles prepared by a conventional mechanical grinding method only reach about 500 nm in diameter and such a method has a serious problem with particle size control. Therefore, the chemical reduction method for preparing silver nano particles is significantly desired. The chemical reduction method involves adding a reduction to agent into silver nitrate solutions to make silver ion in the solutions gain an electron to be reduced to silver with a specific nano particle size as necessary. However, the particle size of the nano silver particles manufactured by the IPA system is about 20 nm or less and the particles in this size would induce a serious bio-toxic effect on the human body and beneficial bacteria existing in the nature. As a result, in order to overcome the disadvantages of the method mentioned above, a method for preparing nano silver particles with a particle size larger than 30 nm is desired.